1.—Field of the Invention
This invention relates to the use of a vehicle Charge Air Cooler (CAC) having an integrated Exhaust Gas Recirculation (EGR) mixer. The integrated Exhaust Gas Recirculation mixer is located either at the inlet, at the inlet manifold, at the outlet, or at the outlet manifold of the Charge Air Cooler. The vehicle Charge Air Cooler having an integrated Exhaust Gas Recirculation mixer may be utilized in a vehicle employing a conventional air to coolant Exhaust Gas Recirculation cooler, or may be used as the sole means of Exhaust Gas Recirculation cooling.
2.—Description of the Related Art
Multiple cylinder internal combustion reciprocating engines used in ground traveling vehicles operate by drawing in ambient intake air, compressing the air, injecting fuel to create a fuel air mixture, igniting the fuel air mixture, extracting work as the heated combustion byproducts expand, and exhausting the combustion byproducts to the surrounding environment. Ignition of the fuel air mixture in an internal combustion reciprocating engine employing the air standard Otto cycle is achieved by means of a spark plug. Internal combustion reciprocating engines employing the air standard Diesel cycle achieve auto-ignition due to the heat of compression of the fuel air mixture. In order to improve performance and operating efficiency, internal combustion reciprocating engines of both the air standard Otto cycle type and the air standard Diesel cycle type commonly utilize a turbocharger. The turbocharger extracts additional work energy from the exhaust gases of the internal combustion reciprocating engine by means of a turbine through which the exhaust gases are made to flow. The turbocharger is typically mounted directly to the exhaust manifold of the internal combustion reciprocating engine in close-coupled proximity to the exhaust outlets for efficient operation of the turbine. The extracted mechanical energy drives a compressor, which compressor increases the pressure of the ambient air drawn into the internal combustion reciprocating engine.
Due to the compression of the ambient intake air associated with the use of a turbocharger, and the resulting increase in temperature thereof, ground traveling vehicles commonly utilize an air to air heat exchanger, which is referred to as a Charge Air Cooler (CAC). The Charge Air Cooler is located separately from and forward of the internal combustion reciprocating engine. The intake air is conducted from the outlet of the turbocharger to the inlet of the Charge Air Cooler by a pipe or conduit, which pipe or conduit is connected to both the turbocharger and to the Charge Air Cooler by flexible rubber cuffs or hoses. In this way, relative movement between the internal combustion reciprocating engine and the Charge Air Cooler is accommodated. Another pipe or conduit conducts the compressed and cooled intake air from the outlet of the Charge Air Cooler to the intake manifold of the internal combustion reciprocating engine. The Charge Air Cooler itself is generally constructed in such a way that there is an inlet manifold and an outlet manifold. The inlet manifold and the outlet manifold of the Charge Air Cooler are connected by smaller cooling passages, which smaller cooling passages are separated by a distance sufficient for the passage of external cooling air therebetween. The inlet manifold is provided with an inlet opening to which the aforementioned pipe from the turbocharger is connected. The outlet manifold is in the same way provided with an outlet opening to which the aforementioned pipe to the intake manifold of the internal combustion reciprocating engine is connected.
The combustion of the fuel air mixture in an internal combustion reciprocating engine results in combustion byproducts, as noted previously. These byproducts primarily consist of carbon dioxide and water vapor. However, there are myriad other chemical constituents, such as hydrocarbons and oxides of nitrogen. Many of these are undesirable from an environmental standpoint, and therefore measures are taken to reduce their formation and emission. A commonly employed method to reduce internal combustion reciprocating engine emissions is Exhaust Gas Recirculation (EGR). A typical embodiment of Exhaust Gas Recirculation involves a pipe that conducts a portion of the exhaust gases from the exhaust manifold to a mixer pipe located between the Charge Air Cooler outlet and the intake manifold of the internal combustion reciprocating engine. A valve may or may not be employed to control the amount of exhaust gas that is recirculated, and the conditions under which the exhaust gas is allowed to do so. Due to the fact that the exhaust gases are under backpressure prior to their further expansion in the turbine of the turbocharger, Exhaust Gas Recirculation may operate passively, requiring no pump. Often the mixer pipe that is utilized incorporates a venturi to increase the flow of exhaust gas from the exhaust manifold to the intake manifold. Some advanced Exhaust Gas Recirculation systems utilize a turbocharger with variable geometry turbine blades to artificially increase the exhaust gas backpressure in order to further increase the flow of exhaust gas from the exhaust manifold to the intake manifold.
Exhaust gases and combustion byproducts leaving the internal combustion reciprocating engine cylinders do so at extremely high temperatures. Therefore, it is common to provide a gas to liquid heat exchanger, which transfers some of the heat from the exhaust gas to the engine coolant, prior to the introduction of the exhaust gas to the intake air at the exhaust gas recirculation mixer. It is also known to configure the system such that the mixer is located between the turbocharger intake air outlet and the Charge Air Cooler inlet. An example of a system configured in this way may be found in U.S. Pat. No. 6,786,210. It is also known, as in U.S. Pat. No. 6,786,210, to provide a bypass circuit within the Charge Air Cooler, in order to prevent condensation of corrosive combustion byproducts within the Charge Air Cooler under certain operating conditions.